Homodyne Laser Vibrometer With Detectability of Nanoscale Vibration and Adaptability to Reflectivity

Abstract

Homodyne laser vibrometer plays an essential role in the precision vibration measurement, but its application is restricted when measuring subfringe vibration and targets with various reflectivities. In order to achieve the nanoscale vibration measurement and to adapt to various reflectivities, an enhanced homodyne laser vibrometer is presented in this paper. First, an active vibration mechanism (AVM) based on a flexure hinge stimulated by a piezoelectric transducer (PZT) is introduced into the reference arm, with which the parameters for nonlinear error correction can be predetermined, and thereby the measurement of vibration less than quarter wavelength is feasible. Second, an automatic gain module is employed to optimize the intensity of the interference signals, which significantly improves the adaptability to target reflectivity. The experimental results show that the laser vibrometer proposed is capable of measuring vibration with amplitude down to 2 nm and vibration with surface reflectivity down to 0.08%.